Field of the Invention
The present invention relates to a motorcycle, and more particularly, to a motorcycle in which arrangement of a continuously variable transmission in a driving force transmission device is improved.
Description of the Related Art
Patent Document 1 (Japanese Patent Laid-Open No. 2002-19682) discloses a power transmission device of a scooter-type motorcycle. This power transmission device transmits rotational force from a crankshaft to a chain-type transmission mechanism in a swing arm through a V-belt continuously variable transmission mechanism and a clutch mechanism to drive a rear wheel that is rotatably supported by the swing arm.
However, in the power transmission device described in Patent Document 1, the crankshaft, a rotating center shaft of a drive pulley (coaxial with the crankshaft) and a rotating center shaft of a driven pulley (main shaft) of the continuously variable transmission mechanism, and a pivot (drive shaft) of the swing arm, are arranged substantially linearly in a vehicle longitudinal direction.
Thus, if the drive pulley and the driven pulley of the continuously variable transmission mechanism are increased in diameter in order to improve driving performance of a vehicle, a dimension from the crankshaft to the pivot of the swing arm is required to be expanded. As a result, vehicle operability and the like are deteriorated.
Furthermore, in a power transmission device of a motorcycle including a conventional scooter-type motorcycle described in Patent Document 1, a part of the clutch mechanism is positioned below an oil level of lubricant in a crankcase of an engine and is soaked in the lubricant. In such arrangement, if a part of the clutch mechanism is soaked in the lubricant, a response ability of engagement and disengagement of the clutch mechanism is deteriorated, which may cause the vehicle operability to be deteriorated.
In order to prevent such defect, a lubricant discharge device (such as a scavenging pump) is provided to discharge the lubricant in a clutch mechanism so as not to easily soak the clutch mechanism in the lubricant. However, in such addition of the lubricant discharge device not only complicates the structure of the vehicle, but also causes power loss for driving the lubricant driving device, and hence, output performance of the vehicle is deteriorated.